The present Invention relates to a transformer core assembly in an inverter transformer for a cold cathode tube, which comprises a coil bobbin about which a primary winding and a secondary winding of the transformer are wound, and a pair of transformer cores to be inserted into a hollow section within the coil bobbin.
Conventionally, a transformer of the kind referred to above is arranged as, for example, in FIG. 3 of the attached drawings.
In FIG. 3, a transformer 1 comprises a coil bobbin 2 formed into a hollow configuration, a coil 5 having a primary winding 3 and a secondary winding 4 which are successively wound respectively about a pair of winging sections 2a and 2b provided in division with respect to a longitudinal direction of the coil bobbin 2, and a pair of E-type cores 6 and 7 having the same shape or configuration in which central core sections 6a and 7a of respective three (3) core sections 6a, 6b and 6c and 7a, 7b and 7c extending in parallel relation to each other are inserted respectively from both ends of a hollow section 2c within the coil bobbin 2 into the same.
According to the transformer constructed as described above, the core sections 6a, 6b and 6c of the E-type core 6 have respective forward ends thereof which are abutted respectively against the core sections 7a, 7b and 7c of the E-type core 7, thereby forming core gaps G, and the magnetic fluxes generated due to the primary winding 3 reach the secondary winding 4 through magnetic paths which extend respectively from the core sections 6a, 6b and 6c of the E-type core 6 to the core sections 7a, 7b and 7c of the E-type core 7 through the core gaps G. In like manner, the magnetic fluxes generated due to the secondary winding 4 reach the primary winding 3 through magnetic paths which extend respectively from the core sections 7a, 7b and 7c of the E-type core 6 to the core sections 6a, 6b and 6c of the E-type core 6 through the core gaps G. Thus, when voltage is applied to the primary winding 3, current flows through the secondary winding 4 to which a load is connected.
The transformer 1 constructed in this manner, however, has the following problems. That is, since the magnetic paths are spaced from each other respectively by the core gaps G, it is impossible that the magnetic fluxes pass 100% at portions of the respective core gaps G, and enter the opposite core sections so that parts of the magnetic fluxes leak to the air. Thus, a transmitting efficiency from the primary side to the secondary side is reduced. Particularly, since the E-type cores 6 and 7 are the same in shape or configuration as each other, the core gaps G are fixed substantially at a center of the coil bobbin 2 with reference to a longitudinal direction thereof. In many cases, the core gaps G are arranged at a location corresponding to the secondary winding. Accordingly, as magnetic fluxes generated by a magnetomotive force of the secondary winding leak into the air by the core gaps G, the magnetic fluxes are not interlinked with the primary winding, whereby an output efficiency of the transformer 1 is reduced. Thus, voltage produced by the secondary winding is reduced, and the starting ability of the inverter for the cold cathode tube is reduced.